Abstract

Obesity and insulin resistance are associated with altered brain glucose metabolism. Here, we studied brain glucose metabolism
in twenty-two morbidly obese patients before and six months after bariatric surgery. Seven healthy subjects served as controls.
Brain glucose metabolism was measured twice per imaging session: with and without insulin stimulation (hyperinsulinemic euglycemic
clamp) using [18F]FDG scanning. We found that during fasting, brain glucose metabolism was not different between groups. However, the hyperinsulinemic
clamp increased brain glucose metabolism in a wide-spread manner in the obese but not in controls, and brain glucose metabolism
was significantly higher during clamp in obese than in control subjects. After follow-up, 6 months postoperatively, the increase
in glucose metabolism was no longer observed, and this attenuation was coupled with improved peripheral insulin sensitivity
after weight loss. We conclude that obesity is associated with increased insulin-stimulated glucose metabolism in the brain,
and that this abnormality can be reversed by bariatric surgery.